In the manufacture of glassware by the conventional process using an individual section (I.S.) machine, a gob of molten glass is first formed into a parison by either pressing or blowing in a blank or parison-forming mould at one station of the machine. Subsequently, the parison is blown into the final shape of the desired article of glassware in a blow mould at another station of the machine as a result of the application of air under pressure to the inside of the parison. Both moulds are formed with mould parts which are separated to permit removal of a parison or article of glassware and brought together again in a closed position of the mould for formation of the next parison or article.
In this known process, difficulties arise from time to time due to breakage of a parison at the blank station and/or breakage of a parison or an article of glassware in the blow mould. When there is breakage of either the parison or the article as aforesaid, a residue of broken glass ("cullet") can be left in the blank or blow mould and the cullet can prevent the formation of a satisfactory parison or aritcle of glassware in the succeeding cycle of a machine.
Cullet which remains in either the blank mould or the blow mould following breakage or malfunction of the parison-forming or article-shaping process in either the blank mould or the blow mould will cool and harden and may impede the closing of the parts of the blank mould or the blow mould in succeeding cycles of the machine. Unless the presence of such cullet in either the blank mould or the blow mould is quickly detected by the operator of the machine and appropriate action taken to prevent several further cycles of the machine taking place, the presence of the cooled, and therefore hard, cullet in the mould can lead to serious damage to either of the moulds when their operating mechanisms, which generate very considerable forces, attempt to close the mould parts, with a result that the machine may be put out of operation for a considerable period until replacement of the damaged mould can be undertaken. There is thus a loss of manufacturing time while the moulds are replaced and the replacement moulds brought up to the correct working temperature.
It is clearly desirable therefore to provide some means by which the malfunction leading to breakage and formation of cullet which impedes the closing of either the blank mould or the blow mould is immediately detected and action taken to prevent more than one further cycle of operation taking place in at least that mould where the malfunction has occurred.